function randomString(len) {
    len = len || 32;
    var $chars = 'ABCDEFGHJKMNPQRSTWXYZabcdefhijkmnprstwxyz2345678';    /****Ĭ��ȥ�������׻������ַ�oOLl,9gq,Vv,Uu,I1****/
    var maxPos = $chars.length;
    var pwd = '';
    for (i = 0; i < len; i++) {
        pwd += $chars.charAt(Math.floor(Math.random() * maxPos));
    }
    return pwd;
}
document.write(randomString(32));
var c = document.getElementById("c");
var ctx = c.getContext("2d");

c.height = window.innerHeight;
c.width = window.innerWidth;

var chinese = "国子监大型交流论坛";
chinese = chinese.split("");

var font_size = 10;
var columns = c.width/font_size;
//an array of drops - one per column
var drops = [];
for(var x = 0; x < columns; x++)
    drops[x] = 1;
//drawing the characters
function draw()
{
    ctx.fillStyle = "rgba(0, 0, 0, 0.05)";
    ctx.fillRect(0, 0, c.width, c.height);

    ctx.fillStyle = "#0F0"; //green text
    ctx.font = font_size + "px arial";
    //looping over drops
    for(var i = 0; i < drops.length; i++)
    {
        var text = chinese[Math.floor(Math.random()*chinese.length)];
        ctx.fillText(text, i*font_size, drops[i]*font_size);

        if(drops[i]*font_size > c.height && Math.random() > 0.975)
            drops[i] = 0;

        drops[i]++;
    }
}
setInterval(draw, 33);